1. Field of the Invention
The present invention relates to an optical apparatus configured to calculate an object distance.
2. Description of the Related Art
Japanese Patent Laid-Open Nos. (“JPs”) 2011-123339 and 2006-227414 disclose two focus lenses, two drivers each configured to drive a corresponding one of the focus lenses, and a controller configured to control the two drivers. JP 09-197259 discloses a camera that includes a wobbling lens separate from a focus lens in a mountain-climbing autofocus (“AF”), and holds the wobbling lens at the midpoint in the manual focusing.
JPs 2011-123339 and 2006-227414 provide a first driver with a lead screw having a large lead angle for fast driving from the infinity to the close end, and a second driver with a lead screw having a small lead angle for precise driving of a micro driving amount. As a result, the fast and precise AF can also be realized with two types of focus lenses. A fast and precise AF can be realized with two drivers for one focus lens. In this case, the second driver drives the focus lens, and the first driver drives the focus lens and a barrel configured to hold the second driver. The lead angle of the lead screw of each driver is similar to the above one.
The prior art that includes a single focus lens and a single driver optimizes the AF and auto-exposure (“AE”) by calculating an object distance from a detection result of a detector configured to detect the position of the focus lens. However, no calculating method of the object distance has been proposed when two drivers drive the focus lens unit.